I’ve just tested it on my end but failed to reproduce the issue. It’s possible that there’s a conflict on your site. Could you please try to reproduce the issue on one of the WordPress’ stock themes (like Twenty Sixteen) with other plugins deactivated? If it disappears, then you can activate the theme and plugins one by one to see which one causes the issue.
If the issue persists, could you please share the XML export file of your field group so I can test it out on my installation?
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